Crane booms,particularly mobile crane booms



Nov. 11, 1969 s. s. THALIN 3,477,539

CRANE BOOMS, PARTICULARLY MOBILE CRANE BOOMS Filed Aug. 23, 1967 INVENTOR ATTORNEYS United States Patent US. Cl. 212-59 2 Claims ABSTRACT OF THE DISCLOSURE A crane having a vertically pivotable boom is supported at its outer end by movable tie cables. To limit lateral bowing of the boom, a retention member is secured to the boom and projects adjacent to the tie cables and is engaged thereby in response to initial bowing of the boom for any position of said tie cables with respect to said boom.

To keep pace with the general aspirations of the building technology in the direction of ever greater building heights, the crane designers are compelled to try to increase the hoisting height of the cranes, particularly that of the mobile cranes. In consequence of, among other things, the tendency towards an ever more extensive element building, in which often big and very heavy elements have to be hoisted, it is also tried to dimension the cranes for ever heavier lifts. For such heavy and high lifts, cranes are often used where the crane boom is in the main subjected to compression.

As the use of mobile cranes for the purpose mentioned increases, the number of crane breakdowns also increases, and in most cases the crane boom is broken laterally a few yards above its attachment. In most cases, the cause of the breakdown is overload in combination with a lack of respect for the lateral forces acting on the crane boom. A detailed discussion of this matter is found in summary in Teknish Tidskrift 1966, No. 20, pp. 495- 497 (Gunnar Thalin). I

The object of the present invention is to reduce the risk of crane breakdowns of the kind mentioned.

To achieve this object, the invention proposes that between its ends the crane boom is provided with a retention member adapted, when the crane boom tends to deflect laterally, to be acted upon transversely of the crane boom by at least one tie cable for the crane boom so that a force preventing an impermissible lateral deflection of the boom is exerted on the boom transversely thereof through the retention member.

In case the crane is provided with two tie cables attached at or near the top of the crane boom, as is most customary nowadays, the rentention member may consist of a preferably detachable frame mounted on the upper portion of the boom and, if desired, movable along the boom, said frame having side portions each disposed outside of and close to one of the tie cables. Alternatively, each side portion of the frame may form a substantially vertical slit in which the associated tie cable is freely movable substantially vertically but confined laterally. This alternative offers the advantage that both tie cables simultaneously contribute to preventing an impermissible lateral deflection of the crane boom.

. 3,477,589 Patented Nov. 11,. 1969 In case only one tiecable is used a single slot is provided which extends iii the vertical longitudinal centre plane and in which the tie cable is movable.

The invention will be described in .more detail below with reference to the accompanying drawing.

FIGURE 1 is a side view of a mobile crane the boom of which is provided witha retention member according to the invention;

FIGURE 2 is a view in cross section through the crane boom taken on the line II--II in FIGURE 1 and showing the retention member as seen along the crane boom;

FIGURE 3 shows amodified embodiment of the'ietention member.

The boom 1 of the mobile crane shown has two tie cables 2 extending from the top of the crane boom over pulleys to machinery on the undercarriage and by means of which the crane boom can be raised and lowered. The hoist cable 3 extends from hoist machinery on the undercarriage around a pulley 4 at the top of the crane boom and to a snatch blocklor crane hook. In its upper part, the crane boom 1 is provided with a retention member 6 mounted on the top side of the boom, detachably if desired, and preferably movable along the boom. The member 6 has the form of -:a frame, at the outside of which the two tie cables are disposed and in which the hoist cable 3 runs. The frame has two vertical side portions 7 parallel to the sides of the crane boom, and when the crane boom is straight,'each side portion 7 isv located immediately adjacent to one of the tie cables 2. When the crane boom is raised and lowered, the tie cables 2 thus slide along the side portions 7.

If the crane boom 1 .-is deflected to one side, the side portion 7 of the frame located opposite to said one side is acted upon by the adjacent tie cable 2 in such a way that a force preventing an impermissible lateral deflection of the boom is exerted on the crane boom transversely thereof.

The retention member shown in FIG. 3 differs from that in FIGURE 2 onlyin that each of the side portions having to be guided longitudinally in the crane boom in some suitable way.

It will be appreciated that the most advantageous position of the retention member in the longitudinal direction of the crane boom can be calculated by a person skilled inthe art considering the length and cross section of the crane boom, loading conditions etc.

What I claim is:

1. In a crane having an upwardly inclined boom, the combination of a pair of horizontally spaced tie cables extending rearwardly above the sides of the boom from the top thereof for varying the inclination of said boom, said .tie cables being maintained under tension under the influence of a load on the boom and forming with the boom an angle varying with the inclination of the boom, and a pair of rigid retention members rigidly secured to the boom rearwardly above the sides thereof and extending between said tie cables and disposed respectively adjacent thereto for being engaged by an adjacent portion of one of said tie cables in response to lateral deflection of said boom and thereby restricting lateral movement of said boom, and enabling tie cable movement vertically with respect to said retention members in response to varying of said angle.

2. A crane according to claim 1, wherein said retention members each define a vertical slot slidably receiving one of said tie cables.

4 References Cited UNITED STATES PATENTS 2,378,915 6/1945 Davidson 212144 2,869,735 1/1959 Page 212-144 2,921,697 1/1960 Holmes 212144 HARVEY C. HORNSBY, Primary Examiner U.S. Cl. X.R. 10 212144 

